But Mr. Crist's steady move to the left — he ran for the Senate as an independent in 2010 — is also clearly a natural curve, boosted by hardball GOP politics, including allegations Crist himself has leveled that GOP hardliners willfully suppressed the vote last month, albeit to no avail.

To be sure, Crist, who served as an Obama surrogate and spoke at the Democratic National Convention, has set himself up as an ideal foil for Republicans both in Florida and nationally, none of whom were surprised at his decision.

Yet Crist's formal declaration as a Democrat, after telling the DNC that "I didn't leave the Republican Party, the Republican Party left me" (echoing Ronald Reagan when the former president left the Democratic Party), still highlights a central GOP post-election conundrum: How to become more, not less, appealing to middle America.

In an interview after the election, Crist pointed to deliberate moves by Republican leaders, including Gov. Scott, to curtail early voting and voter registration efforts, which independent analysts have calculated led to a cumulative 20 percent decrease in early voting hours in some Florida counties.

“After I signed the executive order in [2008] expanding [early voting hours],” Crist told The Palm Beach Post last Sunday, “I heard from Republicans around the state who were bold enough to share it with me that, ‘You just gave the election to Barack Obama.’?”

Crist then added, “I assume they decided, ‘It’s 2011, Crist is gone, let’s give it a shot.' And that’s exactly what they did. And it is exactly what it turned out to be.”

Some conservatives, however, took a different lesson from Crist's decision, namely that the party should welcome the exodus of RINOs, or Republicans-in-name-only: "Crist has acted exactly the way that self-proclaimed moderates within the Republican party typically act," according to an entry on the conservative and widely read Red State blog. "They are willing to be Republicans until they lose a primary challenge and then they quit because 'the Republican party left me.' It also goes to the utter lack of principle that permeates many of our political organization."

But Crist's decision also comes after he tried for years to push Republicans to a more moderate stance — a fight he lost in 2010, both as he lost to a tea party-backed Republican — Marco Rubio — and the rightward turn of the national party as a whole.

At the 2008 Republican Governors Association meeting, which Crist hosted in Miami, he said, "This party can no longer hope to reach Hispanics, African Americans and other minority groups — we need to just do it. Embracing cultures and lifestyles will make us a better party and better leaders. This desire for inclusiveness is near and dear to my heart…."

While Crist has historically been strong on gun rights and has been primarily anti-abortion, his overall record is more liberal. As governor, Crist pushed for stricter air pollution standards and opposed offshore drilling, a position he altered as gas prices rose in 2008. He also reformed state health insurance rules, helping to expand benefits for disabled people and low-income residents.

"I've had friends for years tell me, 'You know Charlie, you're a Democrat and you know it,'" Crist told the Tampa Bay Times.

Yet Crist's convictions will be easy for Republicans to highlight, as they already have, blaming his policies in large part for Florida's economic downturn.

"Charlie Crist's first official act as a Democrat was to tell a lie about why he is now pretending to be one," the Republican Party of Florida wrote in a statement on Saturday. "The truth is that this self-professed, Ronald-Reagan Republican only abandoned his pro-life, pro-gun, conservative principles in 2010 after he realized that Republicans didn't want to send him to Washington D.C. as a senator, especially after he proved he couldn't do the job as governor."